Rapid detection of the aspergillosis biomarker triacetylfusarinine C using interference-enhanced Raman spectroscopy

Susanne Pahlow,Olga Žukovskaja,Thomas Bocklitz,Hubertus Haas,Karina Weber,Thomas Orasch

doi:10.1007/s00216-020-02571-2

Abstract

Triacetylfusarinine C (TAFC) is a siderophore produced by certain fungal species and might serve as a highly useful biomarker for the fast diagnosis of invasive aspergillosis. Due to its renal elimination, the biomarker is found in urine samples of patients suffering from Aspergillus infections. Accordingly, non-invasive diagnosis from this easily obtainable body fluid is possible. Within our contribution, we demonstrate how Raman microspectroscopy enables a sensitive and specific detection of TAFC. We characterized the TAFC iron complex and its iron-free form using conventional and interference-enhanced Raman spectroscopy (IERS) and compared the spectra with the related compound ferrioxamine B, which is produced by bacterial species. Even though IERS only offers a moderate enhancement of the Raman signal, the employment of respective substrates allowed lowering the detection limit to reach the clinically relevant range. The achieved limit of detection using IERS was 0.5 ng of TAFC, which is already well within the clinically relevant range. By using an extraction protocol, we were able to detect 1.4 μg/mL TAFC via IERS from urine within less than 3 h including sample preparation and data analysis. We could further show that TAFC and ferrioxamine B can be clearly distinguished by means of their Raman spectra even in very low concentrations.

Highlights

Invasive aspergillosis (IA) is one of the most common invasive fungal infections, mainly affecting immunocompromised patients and predominantly caused by the mold Aspergillus fumigatus [1]
As a first step towards establishing a protocol for the spectroscopic detection of the biomarker Triacetylfusarinine C (TAFC), reference spectra were recorded, since neither Raman spectra of the iron complex nor the corresponding desferri form exist in the literature to date
Raman spectra of desferrioxamine B (DesfB) and its iron complex (ferrioxamine B (FerB)) were recorded, because this siderophore is structurally related to TAFC [42]

Summary

Introduction

Invasive aspergillosis (IA) is one of the most common invasive fungal infections, mainly affecting immunocompromised patients and predominantly caused by the mold Aspergillus fumigatus [1]. This severe infection is associated with 90day mortality rates of more than 60% depending on the patient cohort [2]. One reason for these high mortality rates is the challenging diagnosis of Aspergillus infections. Biomarkers focuses mainly on Aspergillus cell wall components like galactomannan or 1,3-β-D-glucan. Antimold prophylaxis is widely applied to patients at risk, which further decreases the sensitivity of the employed diagnostic tests [3, 4]

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